DEPENDENCE OF THE REFRACTIVE POWER OF ND-YAG RODS ON THE INTRACAVITY INTENSITY

The refractive power of two flashlamp-pumped Nd:YAG rods was measured as being dependent on the output coupling of the resonator. With laser oscillation, the refractive power or thermal heat is decreased by up to 15% and a minimum occurs at a specific output coupling. The experim ental results could be explained by a theoretical model assuming a non -radiative transition from the upper laser level to the ground state. The lifetime of this non-radiative transition decreases with increasin g pumping power per pulse and, for pumping power higher than 100 kW, s aturation at a value of 0.63 times the fluorescence lifetime occurs. T he results indicate that the non-radiative process is caused by energy migration to flashlamp-induced transient quenching centres.